Bones are held together by cartilage, and cartilage decays and vanishes along with the other soft tissues. So no, skeletons don't hold together by themselves. Skeletons in museums and such are generally held together by wire and glue.
Bones are connected to each other by ligaments which are composed primarily of collagen. After a sufficient period of time the ligaments will decompose and the skeletal remains will be reduced to individual bones.
From Wikipedia, the free encyclopedia
Ligamentum (Plural: Ligamenta)
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